Characteristics of Plasticizers

All moderately high molecular weight liquids or low melting solids or esters of 

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Creep. The creep characteristic of plastic foams must be considered when they are used in stmctural appHcations. Creep is the change in dimensions of a material when it is maintained under a constant stress. Data on the deformation of polystyrene foam under various static loads have been compiled (158). There are two types of creep in this material short-term and long-term. Short-term creep exists in foams at all stress levels however, a threshold stress level exists below which there is no detectable long-term creep. The minimum load required to cause long-term creep in molded polystyrene foam varies with density ranging from 50 kPa (7.3 psi) for foam density 16 kg/m (1 lb /ft ) to 455 kPa (66 psi) at foam density 160 kg/m (10... 

Plastics. Almost all commercial plastics find some use both dry and lubricated for sliding at low speeds and light loads the most commonly used thermoplastics are nylon, acetal resins, and polytetrafluoroethylene (PTFE). Typical thermosetting resins for bearing appHcations are phenoHcs, polyesters, and polyimides. Table 8 compares the characteristics of plastic bearing materials with those of graphite, wood, and mbber which find use in somewhat similar appHcations. 

Many methods have been evolved in recent years for assessing flame retardants and the combustion characteristics of plastics and these have been the subject of comprehensive reviews. " ... 

Thermoplastic polyurethane (TPU) is a type of synthetic polymer that has properties between the characteristics of plastics and rubber. It belongs to the thermoplastic elastomer group. The typical procedure of vulcanization in rubber processing generally is not needed for TPU instead, the processing procedure for normal plastics is used. With a similar hardness to other elastomers, TPU has better elasticity, resistance to oil, and resistance to impact at low temperatures. TPU is a rapidly developing polymeric material. 

The majority of tests to evaluate the characteristics of plastics are performed in tension or flexure hence, the compressive stress-strain behavior of many plastics is not well described. Generally, the behavior in compression is different from that in tension, but the stress-strain response in compression is usually close enough to that of tension so that possible differences can be neglected (Fig. 2-19). The compression modulus is not always reported, since defining a stress at... 

Friction coefficients will vary for a particular material from the value just as motion starts to the value it attains in motion. The coefficient depends on the surface of the material, whether rough or smooth, as well as the composition of the material. Frequently the surface of a particular plastics will exhibit significantly different friction characteristics from that of a cut surface of the same smoothness. These variations and others that are reviewed make it necessary to do careful testing for an application which relies on the friction characteristics of plastics. Once the friction characteristics are defined, however, they are stable for a particular material fabricated in a stated manner. 

In computing ordinary short-term characteristics of plastics, the standard stress analysis formulas may be used. For predicting creep and stress-rupture behavior, the method will vary according to circumstances. In viscoelastic materials, relaxation data can be used in Eqs. 2-16 to 2-20 to predict creep deformations. In other cases the rate theory may be used. 

Under these circumstances it is both tempting and common practice for designers to treat plastics as though they were traditional materials and to apply familiar design methods with what seem appropriate materials constants. It must be admitted that this pragmatic approach does often yield acceptable results. However, it should also be recognized that the mechanical characteristics of plastics are different from those of metals, and the validity of this pragmatic approach is often fortuitous and usually uncertain. 

The non-Newtonian behavior of a plastic melt makes its flow through a die somewhat complicated. One characteristic of plastic is... 

Published by the Plastics Design Library, PDLCOM is an exhaustive reference source of how exposure environments influence the physical characteristics of plastics. Data include resistance to thousands of chemicals, weathering and UV exposure (i.e. color change after accelerated weathering or outdoor exposure) sterilization (radiation, ethylene oxide, steam, etc.) thermal air and water aging environmental stress cracking and much more. 

ASTM, Standard Test Method for Determination of External Loading Characteristics of Plastic Pipe by Parallel-Plate Loading, ASTM D2412-02, American Society for Testing and Materials, West Conshohocken, PA, 2002. 

This book focuses on the relationships between the chemical structure and the related physical characteristics of plastics, which determine appropriate material selection, design, and processing of plastic parts. The book also contains an in-depth presentation of the structure-property relationships of a wide range of plastics, including thermoplastics, thermosets, elastomers, and blends. 

Smith, N. M. and Parnaby, ]., Bulk Density Versus Hydrostatic Pressure Characteristics of Plastics in Powder and Pellet Form, Polym. Eng. Sci., 20, 830 (1980)... 

Two characteristics of plastics are processability and cost. Processing is a key factor required to commercialize a product. A process must be developed to scale up economically from bench to pilot plant and eventually to a production process. Equally important is adaptation of new polymer to economical fabrication. Successful fabrication insures that laboratory properties are inherent in end product. A processability value must be included in initial objectives and product description. 

Combines plastics with chrome, nickel and other metals analogous to chrome plated zinc die cast parts Combines some of the best characteristics of plastics and metals. 

ASTM D1434, 1982 (2003). Standard test method for determining gas permeability characteristics of plastic film and sheeting. 

Processability. The term is used generally to describe the flow characteristics of plastic materials during fabrication. 

ASTM D 7309 Standard Test Method for Determining Flammability Characteristics of Plastics and Other Solid Materials Using Microscale Combustion. Annual Book of Standards, Vol. 08.03, ASTM International, West Conshohocken, PA. 

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